The normal function of the SDF-CXCR4 axis during development of the immune response, is to mediate migration of select hematopoietic, neuronal, and/or cardiovascular cells. The abnormal acquisition of functional CXCR4 receptors in several cancers, unmasks an ability of non-motile tumor cells to migrate and invade into SDF-expressing organs. These processes promote metastasis, the major cause of mortality in cancer patients. Therefore, developing strategies for CXCR4 inhibition are of great interest. In addition to the development of small molecule antagonists and neutralizing antibodies, vigorous attempts have been made to identify therapeutic targets that are required for CXCR4-mediated metastasis. We recently identified ARF6, a monomeric G protein of the Ras superfamily, as a novel regulator of CXCR4 trafficking and signaling. The proposed research specifically addresses an ARF6 requirement for CXCR4 functions which are dependent on SDF gradient sensing, including directional motility and differential signaling kinetics. This research will provide mechanistic insight into the acquisition of a metastatic phenotype, and will advance the establishment of ARF6 as a novel therapeutic target in aggressive CXCR4-expressing cancers. Aberrant CXCR4 expression was initially identified in breast carcinoma. However, CXCR4 has now been shown to be dysregulated in up to 23 different cancers including prostate carcinoma, melanoma, and neuroblastoma, greatly broadening the implications and future directions of the proposed research. Notably, breast and prostate carcinoma currently have the highest incidence and the second highest mortality rates. PUBLIC HEALTH RELEVANCE: The proposed research will significantly advance the establishment of a novel cancer therapeutic target, and provide mechanistic insight into the process of metastasis. Metastasis is the major cause of mortality in cancer patients. Therefore, this research will impact cancer-related health conditions.